Ok, this is actually more a checklist of typical character types that make me hate gamers, but to make it fit the table format, the GM could roll randomly during character creation and spot-check characters to make sure they don't suck.

Any super-hero whose power involves bodily fluids

A mad bomber

A character with an incoherent collection of seemingly random traits/abilities

Any character entirely based on a jokey name/schtick

The same character in every game

A character with no sympathetic traits

Any character you can't describe without referencing stats or equipment

A character whose most interesting story arc has already happened

A gritty loner who doesn't work well with others

A character the rest of the party has absolutely no reason to trust/work with other than the fact he's a PC.

Like, a totally hot ninja chick with huge tits

A character with more weapons than friends

A character belonging to a race with a hive mind

A character with no discernible personality

A character with a weakness guaranteed to constantly sidetrack the game

Another goddamn elf

A character with unexplained and completely out-of-place combat abilities/supernatural knowledge/magical powers